There is a problem with the deployment of a branch stent graft from a main stent graft into a side artery for instance. If a branch stent graft is made substantially flexible, that is, for instance, manufactured with all self expanding stents, then there is a danger that, where a graft extends from a main graft through an aneurysed space within, for instance an aneurysed aorta and then into a side branch artery, such as a renal artery, as the main graft moves the side branch can kink which can close off the lumen through the branch stent graft.
If, however, an essentially rigid stent graft such as a balloon expandable graft is used then the distal end of the stent graft can cause significant distortion of the side branch vessel and there can be a considerable problem with fibrosis, stenosis or damage to the side branch artery at the distal end of the stent graft.
Applicant has found that this problem can be solved by providing greater flexibility of the branch stent graft within the side branch but having a degree of rigidity in the main vessel region.
There is also a problem with holding the branch stent graft into a fenestration in a main graft and this present invention proposes ways to satisfy this requirement.
There can also be problems with stenosis at the distal end of the side graft and this invention proposes methods by which ingrowth at the end of a balloon expandable stent can be reduced.